It's actually a feature :tu:. You can check your Owner's Manual and a search here will also turn up many other threads on this topic. Let us know if you need help finding the description in the Manual.
Since you're a TS Subscriber, you can obtain a pdf version of the Owner's Manual by finding it on the TS Knowledge Base. Comes in pretty handy when you don't want to run get the paper one out of the truck, and sometimes easier to search through as well.How to start the engine——Cranking hold function (with automatic transmission)
Once you turn the ignition key to “START” position and release it, the cranking hold function continues to crank the engine in “ON” position until it starts. The function stops cranking the engine after about 25 seconds maximum if the engine has not started yet. When you crank the engine again, wait a few seconds and restart it. If you hold the key in “START” position, the function will keep cranking for about 30 seconds maximum.